"My boyfriend and I have only had sex twice, but when we do, I bleed afterward. Is this normal?"

Nicole, 17, Nova Scotia, Canada

Some girls bleed the first time they have sex because the hymen, a very thin piece of skinlike tissue that stretches partly across the opening of the vagina, breaks or tears. Some girls are born without much of a hymen. Other girls' hymens cover a large portion of the vagina's opening — it all depends on the girl.

If bleeding happens when you've already had sex before, it may be from irritation or scratching (like from your partner's fingernails) or some further tearing of the remnant of the hymen. But bleeding can also be from a sexually transmitted disease (STD) or other medical problem. If the bleeding continues to happen or if you have any other unexpected symptom, see a doctor. And, of course, now that you are having sex, use a condom every time to help protect against pregnancy and STDs.